Syria has claimed that a constitutional referendum held on Sunday was approved by close to 90% of voters, even as international reaction to its ongoing crackdown intensified, with the European Union announcing fresh sanctions against key regime figures.

Bloodshed continued in restive parts of the country on Monday. Activist groups said 124 people had been killed the day after the ballot, which had been hailed as a showpiece of reform in the rigidly controlled state. The death toll could not be independently verified.

The Baba Amr district of the country's third city, Homs, was again the worst affected, with up to 64 people said to have been killed while trying to flee the area on Monday. Efforts to evacuate a large number of wounded from the embattled neighbourhood – among them two western reporters injured during a rocket attack that killed the Sunday Times correspondent Marie Colvin and French photographer Rémi Ochlik last Wednesday – continued, and ambulances from the Syrian Red Crescent organisation had re-entered Baba Amr yesterday.

The International Committee for the Red Cross has being trying to negotiate a safe exit from Baba Amr for the five days, but efforts have been frustrated by the ongoing military assault on the area and deep distrust between regime and opposition forces.

Syrian officials said 57% of citizens took part in Sunday's referendum, which aimed to remove the Ba'ath party from its pre-eminent position in Syrian society and open up future elections to multiparty candidates. The referendum also aims to impose a two-term – or 14-year – cap on the term of a president, a change that will not be imposed retrospectively, meaning Bashar al-Assad could remain as the country's leader from an election mooted in 2014 until 2028.

The Council of the European Union said new sanctions would be imposed on Syrian government ministers, denying them entry to the EU and freezing assets of the Syrian Central Bank held in the EU.

The new sanctions also deny Syrian cargo planes access to EU airports and ban trade with Syria involving precious metals and diamonds.

"Today's decisions will put further pressure on those who are responsible for the ruthless campaign of repression in Syria," Catherine Ashton, the EU foreign policy chief, said in a statement on Monday. "The measures target the regime and its ability to conduct the appalling violence against civilians. As long as the repression continues, the EU will keep imposing sanctions."

"We need to get the Assad regime to stop killing the population and we need to find ways in which, for the right reasons, that comes about as swiftly as possible," Ashton said. "In our perspective, it's very straightforward – you cannot lead your people, murder them and remain in leadership."

The Syrian referendum has been described as meaningless by opposition groups, Turkey, the US and European states. All diplomatic efforts to force the regime to stop its relentless crackdown on dissent have failed, most noticeably two high-profile attempts via the UN security council, which were vetoed by key allies of Damascus, Russia and China.

A conference, dubbed the Friends of Syria, held in Tunisia over the weekend, partly to bypass the failed UN process, has also failed to bring a halt to the crackdown, which is thought to have killed more than 7,000 citizens as well as more than 2,000 members of the security forces.

The conference called for an urgent ceasefire and the establishment of a humanitarian corridor to allow food and medicines to reach battle-hit areas in the west and north of the country.